Mattermost-server: Improve the design and layout of email notifications

[mattermod]

Summary:
Update the styling for email notifications to make them more friendly looking, helpful and informative to users.

(Optional) this may a helpful tool to do this: https://mjml.io/

The email template design was updated for the following email types:

1. Receiving a Direct Message
2. Being Mentioned in a channel
3. Receiving a Batched email notification
4. Password Reset Email
5. Verification Email
6. You've Joined a Team email
7. Invitation Email
8. Invitation Email for Guests

Figma Design File: https://www.figma.com/file/xMMUFcqIFlyiJlIhLMlcWX/MM-22844-Email-Notification-Redesign?node-id=0%3A1

Sample Email UI Updates

DM Notification

Mention Notification

Batch Notifications

Proposed Updates as seen above:

• Display previews of posts more like they display in the product
• Include the avatar with post content
• Include attached images with post content
• Update headline and body copy
• Add a more slightly more obvious link to change notification preferences
• Refreshes UI overall
• Uses Open Sans webfont, with Arial fallback

Note: Some of the cloud emails follow similar layout for the top portion of the email. Implementation could benefit from leveraging this previous work.

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JIRA: https://mattermost.atlassian.net/browse/MM-22844

[jp0707]

I would like to work on this. Are there any docs explaining current email rendering infra? Could someone give me couple of pointers to the appropriate code for rendering emails locally?

[esethna]

Thanks @jp0707!
@hmhealey can you help provide any guidance here or point us to another dev with knowledge in this area?

[esethna]

Or @matthewbirtch do you know what dev worked on the cloud emails that could provide some guidance here?

[matthewbirtch]

Or @matthewbirtch do you know what dev worked on the cloud emails that could provide some guidance here?

@nickmisasi has worked a fair bit on emails for Cloud. Just a note though, the email updates here aren't in cloud yet. The cloud emails might be a good starting point though

[esethna]

Thanks. @nickmisasi would you be able to provide some guidance here for @jp0707 that help get her started implementing these email UI updates as per her comment above?

[nickmisasi]

@esethna Sure, I'll provide some detail below. Love the idea of using the framework for these, as I think it'd be super helpful (emails are annoying to get to look proper in all clients, and then having them be responsive is even harder). However, I think there would need to be some input from core teams into how we implement that framework into our core product.

@jp0707 you can find all of our existing email templates here: https://github.com/mattermost/mattermost-server/tree/master/templates
We use Golang's built-in HTML templating engine, and populate the various values in the app layer here: https://github.com/mattermost/mattermost-server/blob/master/app/email.go. Most emails sent out of mattermost are sent via functions in that file.
Our email notification templates are fairly primitive, they are styled mostly in-line and use table layouts. If you have any other questions feel free to @ me here or shoot me a DM on the Mattermost community server!

[jp0707]

@nickmisasi : Here's a proof of concept with welcome email: https://github.com/jp0707/mattermost-server/commit/d372e09bc6cb3f3eb766d578f0acabd7823732a2 . The email still lacks style polishing, but this is meant to be proof of concept for mjml + Go templating.

Here's how it works:

1. Emails are written in mjml with Go's html/template annotation.
2. At build time, mjml templates are compiled into html templates. Compiled templates are stored inside templates/compiled directory.
3. Mechanism for reading/parsing and rendering the emails support both old and new emails. This allows us to move over emails gradually to mjml.

Please take a look. I'd love to have core team look at this and give their feedback. Who/where should I ask for core team's feedback?